Have a bit of spotting? Light, brief (lasting just a day or two) spotting can actually be a sign of early pregnancy. It’s known as “implantation bleeding,” and here’s what it means: A few days after conception, that little fertilized (yay!) egg starts digging into the wall of your uterus and getting ready to grow. Since the uterine lining is nice and rich with blood, some women spot a little at this point. This is totally normal and no cause for concern but a pregnancy test and doctor's visit is in order to make sure implantation bleeding is truly the culprit.
There aren't reliable stats on how many women actually experience implantation bleeding. Some do, some don't. And some claim it lasts for one day; others say three or four. All in all, there's no real way to know whether spotting (or lack thereof) indicates pregnancy. Only a test can tell.
If you find yourself bleeding heavily or for more than a couple of days, or if you bleed during a later stage of your pregnancy, call your doctor right away. This could be a sign of miscarriage or an ectopic (often called “tubal”) pregnancy.